/*
 * Dynomite - A thin, distributed replication layer for multi non-distributed storages.
 * Copyright (C) 2014 Netflix, Inc.
 */ 

/*
 * twemproxy - A fast and lightweight proxy for memcached protocol.
 * Copyright (C) 2011 Twitter, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <dyn_core.h>
#include <dyn_server.h>
#include <dyn_hashkit.h>

#define KETAMA_CONTINUUM_ADDITION   10  /* # extra slots to build into continuum */
#define KETAMA_POINTS_PER_SERVER    160 /* 40 points per hash */
#define KETAMA_MAX_HOSTLEN          86

/*static uint32_t
ketama_hash(const char *key, size_t key_length, uint32_t alignment)
{
    unsigned char results[16];

    md5_signature((unsigned char*)key, key_length, results);

    return ((uint32_t) (results[3 + alignment * 4] & 0xFF) << 24)
        | ((uint32_t) (results[2 + alignment * 4] & 0xFF) << 16)
        | ((uint32_t) (results[1 + alignment * 4] & 0xFF) << 8)
        | (results[0 + alignment * 4] & 0xFF);
}

static int
ketama_item_cmp(const void *t1, const void *t2)
{
    const struct continuum *ct1 = t1, *ct2 = t2;

    if (ct1->value == ct2->value) {
        return 0;
    } else if (ct1->value > ct2->value) {
        return 1;
    } else {
        return -1;
    }
}*/

rstatus_t
ketama_update(struct server_pool *pool)
{
    /* uint32_t nserver;             /\* # server - live and dead *\/ */
    /* uint32_t nlive_server;        /\* # live server *\/ */
    /* uint32_t pointer_per_server;  /\* pointers per server proportional to weight *\/ */
    /* uint32_t pointer_per_hash;    /\* pointers per hash *\/ */
    /* uint32_t pointer_counter;     /\* # pointers on continuum *\/ */
    /* uint32_t pointer_index;       /\* pointer index *\/ */
    /* uint32_t points_per_server;   /\* points per server *\/ */
    /* uint32_t continuum_index;     /\* continuum index *\/ */
    /* uint32_t continuum_addition;  /\* extra space in the continuum *\/ */
    /* uint32_t server_index;        /\* server index *\/ */
    /* uint32_t value;               /\* continuum value *\/ */
    /* uint32_t total_weight;        /\* total live server weight *\/ */
    /* int64_t now;                  /\* current timestamp in usec *\/ */

    /* ASSERT(array_n(&pool->server) > 0); */

    /* now = dn_usec_now(); */
    /* if (now < 0) { */
    /*     return DN_ERROR; */
    /* } */

    /* /\* */
    /*  * Count live servers and total weight, and also update the next time to */
    /*  * rebuild the distribution */
    /*  *\/ */
    /* nserver = array_n(&pool->server); */
    /* nlive_server = 0; */
    /* total_weight = 0; */
    /* pool->next_rebuild = 0LL; */
    /* for (server_index = 0; server_index < nserver; server_index++) { */
    /*     struct server *server = array_get(&pool->server, server_index); */

    /*     if (pool->auto_eject_hosts) { */
    /*         if (server->next_retry <= now) { */
    /*             server->next_retry = 0LL; */
    /*             nlive_server++; */
    /*         } else if (pool->next_rebuild == 0LL || */
    /*                    server->next_retry < pool->next_rebuild) { */
    /*             pool->next_rebuild = server->next_retry; */
    /*         } */
    /*     } else { */
    /*         nlive_server++; */
    /*     } */

    /*     ASSERT(server->weight > 0); */

    /*     /\* count weight only for live servers *\/ */
    /*     if (!pool->auto_eject_hosts || server->next_retry <= now) { */
    /*         total_weight += server->weight; */
    /*     } */
    /* } */

    /* pool->nlive_server = nlive_server; */

    /* if (nlive_server == 0) { */
    /*     log_debug(LOG_DEBUG, "no live servers for pool %"PRIu32" '%.*s'", */
    /*               pool->idx, pool->name.len, pool->name.data); */

    /*     return DN_OK; */
    /* } */
    /* log_debug(LOG_DEBUG, "%"PRIu32" of %"PRIu32" servers are live for pool " */
    /*           "%"PRIu32" '%.*s'", nlive_server, nserver, pool->idx, */
    /*           pool->name.len, pool->name.data); */

    /* continuum_addition = KETAMA_CONTINUUM_ADDITION; */
    /* points_per_server = KETAMA_POINTS_PER_SERVER; */
    /* /\* */
    /*  * Allocate the continuum for the pool, the first time, and every time we */
    /*  * add a new server to the pool */
    /*  *\/ */
    /* if (nlive_server > pool->nserver_continuum) { */
    /*     struct continuum *continuum; */
    /*     uint32_t nserver_continuum = nlive_server + continuum_addition; */
    /*     uint32_t ncontinuum = nserver_continuum * points_per_server; */

    /*     continuum = dn_realloc(pool->continuum, sizeof(*continuum) * ncontinuum); */
    /*     if (continuum == NULL) { */
    /*         return DN_ENOMEM; */
    /*     } */

    /*     pool->continuum = continuum; */
    /*     pool->nserver_continuum = nserver_continuum; */
    /*     /\* pool->ncontinuum is initialized later as it could be <= ncontinuum *\/ */
    /* } */

    /* /\* */
    /*  * Build a continuum with the servers that are live and points from */
    /*  * these servers that are proportial to their weight */
    /*  *\/ */
    /* continuum_index = 0; */
    /* pointer_counter = 0; */
    /* for (server_index = 0; server_index < nserver; server_index++) { */
    /*     struct server *server; */
    /*     float pct; */

    /*     server = array_get(&pool->server, server_index); */

    /*     if (pool->auto_eject_hosts && server->next_retry > now) { */
    /*         continue; */
    /*     } */

    /*     pct = (float)server->weight / (float)total_weight; */
    /*     pointer_per_server = (uint32_t) ((floorf((float) (pct * KETAMA_POINTS_PER_SERVER / 4 * (float)nlive_server + 0.0000000001))) * 4); */
    /*     pointer_per_hash = 4; */

    /*     log_debug(LOG_VERB, "%.*s:%"PRIu16" weight %"PRIu32" of %"PRIu32" " */
    /*               "pct %0.5f points per server %"PRIu32"", */
    /*               server->name.len, server->name.data, server->port, */
    /*               server->weight, total_weight, pct, pointer_per_server); */

    /*     for (pointer_index = 1; */
    /*          pointer_index <= pointer_per_server / pointer_per_hash; */
    /*          pointer_index++) { */

    /*         char host[KETAMA_MAX_HOSTLEN]= ""; */
    /*         size_t hostlen; */
    /*         uint32_t x; */

    /*         hostlen = snprintf(host, KETAMA_MAX_HOSTLEN, "%.*s-%u", */
    /*                            server->name.len, server->name.data, */
    /*                            pointer_index - 1); */

    /*         for (x = 0; x < pointer_per_hash; x++) { */
    /*             value = ketama_hash(host, hostlen, x); */
    /*             pool->continuum[continuum_index].index = server_index; */
    /*             pool->continuum[continuum_index++].value = value; */
    /*         } */
    /*     } */
    /*     pointer_counter += pointer_per_server; */
    /* } */

    /* pool->ncontinuum = pointer_counter; */
    /* qsort(pool->continuum, pool->ncontinuum, sizeof(*pool->continuum), */
    /*       ketama_item_cmp); */

    /* for (pointer_index = 0; */
    /*      pointer_index < ((nlive_server * KETAMA_POINTS_PER_SERVER) - 1); */
    /*      pointer_index++) { */
    /*     if (pointer_index + 1 >= pointer_counter) { */
    /*         break; */
    /*     } */
    /*     ASSERT(pool->continuum[pointer_index].value <= */
    /*            pool->continuum[pointer_index + 1].value); */
    /* } */

    /* log_debug(LOG_VERB, "updated pool %"PRIu32" '%.*s' with %"PRIu32" of " */
    /*           "%"PRIu32" servers live in %"PRIu32" slots and %"PRIu32" " */
    /*           "active points in %"PRIu32" slots", pool->idx, */
    /*           pool->name.len, pool->name.data, nlive_server, nserver, */
    /*           pool->nserver_continuum, pool->ncontinuum, */
    /*           (pool->nserver_continuum + continuum_addition) * points_per_server); */

    return DN_OK;
}

uint32_t
ketama_dispatch(struct continuum *continuum, uint32_t ncontinuum, uint32_t hash)
{
    struct continuum *begin, *end, *left, *right, *middle;

    ASSERT(continuum != NULL);
    ASSERT(ncontinuum != 0);

    begin = left = continuum;
    end = right = continuum + ncontinuum;

    while (left < right) {
        middle = left + (right - left) / 2;
        if (middle->value < hash) {
          left = middle + 1;
        } else {
          right = middle;
        }
    }

    if (right == end) {
        right = begin;
    }

    return right->index;
}
